Method for improving the qos mechanisms in the bandwidth allocation in cdma mobile communication systems

ABSTRACT

The invention relates to a method for improving QoS mechanisms during bandwidth allocation in CDMA mobile communication systems, characterized in that the user terminal signals the minimal bandwidth (bit rate) which is required to the mobile communication system and a bandwith within said range is allocated to the radio interface when available. As a result, the opportunities provided by the user terminal and the bandwith available in the radio cell are used as efficiently as possible.

The invention relates to a method for improving the QoS (Quality ofService) mechanisms in the bandwidth allocation in CDMA mobilecommunication systems, such as e.g., a UMTS mobile communication system.

A UMTS network is composed of a plurality of radio network subsystems(RNS). Each RNS consists of a radio network controller (RNC) and one ora plurality of nodes B. A node B contains one or a plurality of radiostations, each of which cover one radio cell (sector). The RNC takes onthe control for handover and the functions in connection withmacrodiversity between different nodes B. The individual RNS themselvescan exchange data among themselves directly via the corresponding RNC.The connection of the nodes B to their RNC takes place via a Uuinterface.

A node B administers a group of radio cells, which may be operated inFDD mode, TDD mode, or in both duplex modes. It is capable ofcontrolling soft handover and macrodiversity within its cellsindependently from the RNC. The purpose of the signaling procedure liesin the establishment of a Radio Access Bearer from the CN to the endunit. For this purpose the RAB ASSIGNMENT REQUEST message contains theestablished RAB-ID, as well as all necessary routing parameters and thedesired quality of service (QoS). It is possible to negotiate a QoS; inthis case the response RAB ASSIGNMENT RESPONSE contains the actual QoSallocated to this RAB. The message RAB ASSIGMENT REQUEST is always sentfrom the CN and can, in addition to establishing a RAB, also be used forits modification or release. With a single procedure, a plurality ofRABs can be established to a subscriber end unit. A RAB thus representsa user data channel through the UMTS network to the subscriber end unit.

A UMTS TD-CMDA system comprises 64 speech channels per carrier. Withthese 64 channels, different data rates from 9.6 kbit/s to 2 Mbit/s cannow be flexibly adjusted by combining the channels accordingly.

According to the method for activating a so-called Packet Data Protocolcontext (PDP context), as it can be found in the specification ETSI TS123 207 V5.5.0 (2002-09), “Digital Cellular Telecommunications System(Phase 2+), Universal Mobile Telecommunications System (UMTS), End toEnd Quality of Service (QoS) Concept and Architecture”, 3GPP TS 23.207,the subscriber end unit sends the message ACTIVATE PDP CONTEXT REQUEST,which contains the requested QoS parameters. The contained QoSinformation elements, however, up to now comprise only informationregarding the guaranteed bit rate granted to the subscriber end unit andthe maximum bit rate for uplink and downlink. It should be mentioned atthis point that the terms bandwidth, bit rate and data rate within theframework of this invention are used in an equivalent manner.

U.S. Pat. No. 6,069,883A reveals a CDMA mobile radio system with theoption of allocating an increased bandwidth to a mobile stationrequesting this bandwidth. The purpose here is not to guarantee aminimum bandwidth reported by the mobile station, but to make availableto the mobile station the highest possible bandwidth.

EP 1 154 663 A1 reveals a method for controlling the Quality of Service(QoS) in a mobile communication network wherein a check is performed foreach new connection regarding whether a desired bandwidth can be madeavailable. In the process, a degradation in the bandwidth of existingconnections is accepted within specified limits, if necessary. Aso-called QoS descriptor is therefore specified for each connection,which determines by how much the bandwidth allocated to this connectionmay be reduced if required.

It is the object of the invention to create a method for improving theQoS mechanisms in the bandwidth allocation in CDMA mobile communicationsystems whereby the available bandwidth in a radio cell can beoptimized.

This object is met according to the invention with the characteristicsof claim 1.

Advantageous embodiments and improvements of the invention will becomeapparent from the subclaims.

The invention enables a subscriber end unit to signal to the mobilecommunication network which minimum bit rate it requires for downlinkand uplink. Based on the minimum bit rate specified by the end unit andthe maximum bit rate established in the standard, the RNC can optimizethe administration of the available bandwidth. The possibilities of thesubscriber end unit and bandwidth available in the radio cell are thusutilized to the fullest extent possible.

The invention takes as a starting point that a total bandwidth isavailable in each radio cell. Each subscriber end unit that influencesthe radio cell is thus allocated, if possible, a desired or requiredeffective bandwidth. It is now the mission of the resourceadministration to ensure that the sum of the effective bandwidths isalways smaller than the total bandwidth in the radio cell.

In the QoS request, the subscriber end unit specifies the minimum bitrate that is needed by it and by the given application. If the specifiedminimum bit rate is not available on the air interface, the applicationcannot be carried out.

During the PDP context activation, the assigned network node sends themessage RAB ASSIGNMENT REQUEST to the RNC, which, as known up to now,contains the maximum bit rate allocated to the subscriber end unit orair interface, and the guaranteed bit rate for uplink and downlink.

Additionally, this message according to the invention containsinformation regarding the minimum bit rate and maximum bit rate that areavailable to the subscriber end unit and to the given application. Theseminimum and maximum bit rates correspond to the requested bit rates,provided that the necessary bandwidth capacity is available in the radiocell.

The RNC handles the assignment of the RAB (Radio Access Bearer) and ofthe codes in accordance with the requested bandwidth.

In accordance with the invention, the RNC is responsible for theassignment of RAB and bandwidth according to a list of rules that can beestablished and modified by a network operator.

The rules are essentially based on the following input parameters:

-   -   Class of Service    -   Available bandwidth and/or codes    -   The requested maximum bit rate    -   The requested minimum bit rate    -   The requested guaranteed bit rate

Based on these rules a corresponding RAB is assigned to the airinterface.

The rules may be time-dependent. The rules may permit, for example, toallocate higher bit rates to a subscriber end unit during the night,i.e., during a time of reduced traffic loads. The rules may also dependon the given subscriber relationship and/or applied fee schedule.

If sufficient bandwidth (or codes) are available in the radio cell, theallocated bit rate cannot be higher than the “maximum” bit rate, buthigher than the “guaranteed” bit rate specified in the requested QoS, aslong as it is between the minimum and maximum bit rate requested by thesubscriber end unit.

The allocated QoS parameters are then sent back to the subscriber endunit by a network node (e.g., by a SGSN) by means of the message“ACTIVATE PDP CONTEXT ACCEPT”.

The allocated bit rate can also be modified later by means of the“PDP-context modification procedure” defined in the 3GPP (3^(rd)Generation Partnership Project [www.3GPP.org]), e.g., if the remainingavailable bandwidth is requested by other subscribers.

The invention will now be explained in more detail based on a simpleexample.

The following case exists: An air interface of a radio cell, at a pointin time to, has a total available bandwidth of 256 kbit/s.

At the time t0, a user 1 requests a RAB with a guaranteed and maximumbit rate of 64 kbit/s in order to download a file with a size of 256kbit. Following the current rules, as they are defined, e.g., in 3GPP,the RNC assigns to the user a code that corresponds to a bit rate of 64kbit/s. At the requested bit rate, the download is completed in 4seconds, i.e., at the point in time t0+4s.

At the time t0+1s, user 2 and user 3 also request a RAB with aguaranteed bandwidth of 64 kbit/s. These requests can be met.

The remaining bandwidth on the air interface at the time t0+1s is,therefore, 64 kbit/s.

At the time t0+2s, a user 4 requests a RAB with a guaranteed and maximumbit rate of 128 kbit/s. This request can not be met since only abandwidth of 64 kbit/s is currently available on the air interface.

If user 1, however, had signaled to the network at the point in time t0that he is requesting a maximum bandwidth of 128 kbit/s for the downloadof a file of 256 kbit, the RNC would have allocated to the user a codefor 128 kbit/s. Taking into account the bandwidths of 64 kbit/sallocated to each of the users 1 and 2, the download of user 1 wouldhave been completed at the point in time t0+2, and a bandwidth of 128kbit/s would have been available. User 4 could, therefore, have beenallocated the desired bandwidth of 128 kbit/s.

1. A method for improving the QoS mechanisms in the bandwidth allocationin CDMA mobile communication systems, characterized in that thesubscriber end unit signals to the mobile communication system whichminimum bandwidth (bit rate) it requires, and the mobile communicationsystem allocates to the connection to the subscriber end unit abandwidth within the requested range, if available, that a network nodeRNC handles the assignment of a Radio Access Bearer RAB and of the codesaccording to the requested bandwidth, wherein the assignment of RAB andbandwidth takes place according to a number of rules.
 2. A methodaccording to claim 1, characterized in that the bandwidth is requestedwithin the message ACTIVATE PDP CONTEXT REQUEST.
 3. A method accordingto claim 1, characterized in that the allocated QoS parameters are sentback from the network node by means of the message ACTIVATE PDP CONTEXTACCEPT to the subscriber end unit.
 4. A method according to claim 1,characterized in that the rules are based on at least one of thefollowing input parameters: Class of Service, available bandwidth and/orcodes, requested maximum bit rate and/or requested guaranteed bit rate.5. A method according to claim 4, characterized in that the rules aretime-dependent.
 6. A method according to claim 4, characterized in thatthe rules depend on the given subscriber relationship and/or applied feeschedule.
 7. A method according to claim 2, characterized in that theallocated QoS parameters are sent back from the network node by means ofthe message ACTIVATE PDP CONTEXT ACCEPT to the subscriber end unit.